Carbon-coated TiNb2O7 nanosheet arrays as self-supported high mass-loading anodes for flexible Li-ion batteries

Ultrathin Carbon-Coated Porous TiNb2O7 Nanosheets as Anode Materials for Enhanced Lithium Storage

TiNb₂O₇ has been considered as a promising anode material for next-generation high power lithium ion batteries for its relatively high theoretical capacity, excellent safety and long cycle life. However, the unsatisfactory electrochemical kinetics resulting from the intrinsic sluggish electron transport and lithium ion diffusion of TiNb₂O₇ limit its wide application. Morphology controlling and carbon coating are two effective methods for improving the electrochemical performance of electrode materials. Herein, an ultrathin carbon-coated porous TiNb₂O₇ nanosheet (TNO@C) is successfully fabricated by a simple and effective approach. The distinctive sheet-like porous structure can shorten the transport path of ions/electrons and provide more active sites for electrochemical reaction. The introduction of nanolayer carbon can improve electronic conductivity and increase the specific surface area of the porous TiNb₂O₇ nanosheets. Based on the above synergistic effect, TiNb₂O₇@C delivers an initial discharge capacity of 250.6 mAh g^-1 under current density of 5C and can be maintained at 206.9 mAh g^-1 after 1000 cycles with a capacity retention of 82.6%, both of which are superior to that of pure TiNb₂O₇. These results well demonstrate that TiNb₂O₇@C is a promising anode material for lithium ion batteries.

Pseudocapacitive TiNb2O7/reduced graphene oxide nanocomposite for high-rate lithium ion hybrid capacitors

Lithium ion hybrid capacitors (LIHCs) have a capacitor-type cathode and a battery-type anode and are a prospective energy storage device that delivers high energy/power density. However, the kinetic imbalance between the cathode and the anode is a key obstacle to their further development and application. Herein, we prepared TiNb₂O₇ nanoparticles through a facile solvothermal method and annealing treatment. Then a homogeneous three-dimensional (3D) self-supported reduced graphene oxide (rGO)-coated TiNb₂O₇ (TiNb₂O₇/rGO) nanocomposite was constructed by freeze-drying, followed by a high-temperature reduction, which demonstrates an enhanced pseudocapacitive lithium ions storage performance. Benefiting from the improved electrical conductivity, ultrashort ions diffusion paths, and 3D architecture, the TiNb₂O₇/rGO nanocomposite exhibits a high specific capacity of 285.0 mA h g^-1, excellent rate capability (73.6% capacity retention at 8 A g^-1), and superior cycling stability. More importantly, quantitative kinetics analysis reflects that the capacity of TiNb₂O₇/rGO is mainly dominated by capacitive behavior, making it perfectly match with the capacitor-type activated carbon (AC) cathode. By using pre-lithiated TiNb₂O₇/rGO as anode material and AC as cathode material, a high-rate TiNb₂O₇/rGO//AC LIHC device can be fabricated, which delivers an ultrahigh energy density of 127 Wh kg^-1 at the power density of 200 W kg^-1, a maximum power density of 10 kW kg^-1 at the energy density of 56.4 Wh kg^-1, and durable service life.

Engineering a novel microcapsule of Cu9S5 core and SnS2 quantum dot/carbon nanotube shell as a Li-ion battery anode

A novel microcapsule composed of Cu₉S₅ and SnS₂ quantum dots (QDs)/carbon nanotubes (CNTs) prepared through a microfluidic approach was developed for a Li-ion battery anode. CNTs enhance the conductivity, while pores in the shell facilitate electrolyte penetration, and void in the microcapsule buffers the volume change. The microcapsule-based anode displayed stable capacity, a Coulombic efficiency of 99.9%, and reversible rate-performance at temperatures of -10 °C and 45 °C, which are significant for developing high-performance energy-storage materials and battery systems.